A program for testing the MCP4725 library. This Test Application requires the following: * An MCP4725 connected to the IC2 bus of the mbed LPC1768. * The analog out of the MCP1768 connected to Pin15 (analog in) of the mbed LPC1768. * An optional LED & resistor connected to analog output for visual feedback of the running tests. This application tests the MCP4725 library's setting of the MCP4725's internal registers (including eeprom storage), it's analog output and power modes.

Dependencies:   mbed

Files at this revision

API Documentation at this revision

Comitter:
donalm
Date:
Sun Nov 03 11:22:01 2013 +0000
Parent:
3:e8da8b9d757e
Commit message:
Added feedback test on DAC output.

Changed in this revision

main.cpp Show annotated file Show diff for this revision Revisions of this file
diff -r e8da8b9d757e -r 092580187b59 main.cpp
--- a/main.cpp	Sun Oct 27 14:28:55 2013 +0000
+++ b/main.cpp	Sun Nov 03 11:22:01 2013 +0000
@@ -3,17 +3,25 @@
 #include "mcp4725.h"
 
 /**
- * A basic test suite for the MCP4725 DAC Library.
+ * A test suite for the MCP4725 DAC Library. This Test Application requires the following:
+ *  * An MCP4725 connected to the IC2 bus of the mbed LPC1768.
+ *  * The analog out of the MCP1768 connected to Pin15 (analog in) of the mbed LPC1768.
+ *  * An optional LED & resistor connected to analog output for visual feedback of the running tests.
+ *
+ * This application tests the MCP4725 library's setting of the MCP4725's internal registers (inclusing eeprom storage), 
+ * it's analog output and power modes.
+ *
  */
 
-DigitalOut myled(LED1);
+DigitalOut testLed(LED1);
 Serial pc(USBTX, USBRX);
+AnalogIn analogIn(p15);
 
 void test_mcp4725_library(PinName sda, PinName scl, MCP4725::BusFrequency bus_frequency, int device_address_bits, char* testName);
 int  test_init(MCP4725* interface, char* testName);
-int  test_simple_read_write_no_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, int dac_value);
-int  test_simple_read_write_with_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, int dac_value);
-int test_eeprom_write_status(MCP4725* interface);
+int  test_simple_read_write_no_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, float output_voltage);
+int  test_simple_read_write_with_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, float output_voltage);
+int  test_eeprom_write_status(MCP4725* interface);
 
 int main()
 {
@@ -24,9 +32,9 @@
     test_mcp4725_library(p9, p10, MCP4725::HighSpeed3_4Mhz, 0, "p9, p10, MCP4725::HighSpeed3_4Mhz");
 
     while(1) {
-        myled = 1;
+        testLed = 1;
         wait(0.5);
-        myled = 0;
+        testLed = 0;
         wait(0.5);
     }
 }
@@ -47,17 +55,17 @@
     
     if(test_init(&mcp4725_interface, testName) == 0)
     {
-        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::Normal, 3095);
-        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::PowerDown1k, 2094);
-        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::PowerDown100k, 2093);
-        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::PowerDown500k, 92);
-        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::Normal, 4095);
+        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::Normal, 3.0);
+        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::PowerDown1k, 1.3);
+        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::PowerDown100k, 1.8);
+        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::PowerDown500k, 0.5);
+        test_simple_read_write_no_eeprom(&mcp4725_interface, MCP4725::Normal, 2.5);
         
-        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::Normal, 3095);
-        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::PowerDown1k, 2094);
-        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::PowerDown100k, 2093);
-        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::PowerDown500k, 92);
-        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::Normal, 4095);
+        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::Normal, 3.0);
+        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::PowerDown1k, 1.3);
+        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::PowerDown100k, 1.8);
+        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::PowerDown500k, 0.5);
+        test_simple_read_write_with_eeprom(&mcp4725_interface, MCP4725::Normal, 2.5);
         
         test_eeprom_write_status(&mcp4725_interface);
     }
@@ -87,7 +95,7 @@
 }
 
 /* Run a simple read/write test that does not write to eeprom. */
-int test_simple_read_write_no_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, int dac_value)
+int test_simple_read_write_no_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, float output_voltage)
 {
     enum MCP4725::PowerMode read_mode;
     enum MCP4725::PowerMode read_mode_eeprom;//, write_mode_eeprom;
@@ -95,6 +103,8 @@
     int  read_dac_value_eeprom;//, write_dac_value_eeprom;
     bool read_eeprom_write_in_progress;
     
+    int dac_value = (int) (0xFFF * (output_voltage/3.3) );
+    
     pc.printf("\tRead/write test without write to eeprom: ");
     
     interface->write(mode, dac_value, false);
@@ -106,20 +116,44 @@
     }
     else
     {
-        pc.printf("Passed\r\n");
-        return 0;
+        // We need to wait a short period for the output to stabalise.
+        wait(0.2);
+        
+        /* We check at mV resolution. 
+         * Resolution of 12bit DAC is 0.8mV
+         * Resolution of 16bit ADC is 0.05mV
+         */
+        int read_value_mv = (analogIn.read() * 3.3) * 100;
+        int set_value_mv = ((int)(output_voltage*100));
+        
+        if( (mode == MCP4725::Normal) && (read_value_mv !=  set_value_mv) )
+        {
+            pc.printf("Failed: set_value=%dmV, read_value=%dmV\r\n", read_value_mv, set_value_mv);
+            return 1;
+        }
+        else if ( (mode != MCP4725::Normal) && (read_value_mv != 0) )
+        {
+            pc.printf("Failed: read_value=%dmV, but DAC in PowerDown!\r\n", read_value_mv);
+            return 1;
+        }
+        else
+        {
+            pc.printf("Passed\r\n");
+            return 0;
+        }
     }
 }
 
 
 /* Run a simple read/write test that does write to eeprom. */
-int test_simple_read_write_with_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, int dac_value)
+int test_simple_read_write_with_eeprom(MCP4725* interface, enum MCP4725::PowerMode mode, float output_voltage)
 {
     enum MCP4725::PowerMode read_mode;
     enum MCP4725::PowerMode read_mode_eeprom;//, write_mode_eeprom;
     int  read_dac_value;
     int  read_dac_value_eeprom;//, write_dac_value_eeprom;
     bool read_eeprom_write_in_progress;
+    int dac_value = (int) (0xFFF * (output_voltage/3.3) );
     
     pc.printf("\tRead/write test with write to eeprom: ");